1. Field of the Invention
The present invention provides a method and apparatus for mixing and gasifying a reactant gas-liquid and more particularly a method and device that can provide stable control of a delivery of a reactant gas over a range of flow rates to, for example, a semiconductor production line.
2. Description of Relevant Art
Among the conventional liquid material gasifying apparatus, there is a device which is designed to gasify a liquid material within a three-way control valve equipped with a flow control function, as described, for example, in U.S. Pat. No. 5,419,924. FIG. 9 is a view showing a principal part of this liquid material gasifying apparatus. A control valve 70 is furnished with a flow control function, with a valve body 71 formed with a recess 72. The part 73 is a driving part which is provided to block a portion of the recess 72, and is furnished with a plunger 74 which rises and descends in the recess 72. A valve seat 75 is formed on the upper part of a projection 76 projecting upward from the center of the bottom face of the valve body 71. A flexible diaphragm 77 divides the inside of the recess 72 into an upper space 78 including the plunger 74 and a lower space 79 including the valve seat 75, and the diaphragm 77 is constituted to come into scaling contact with the upper surface of the valve seat 75 by the descending of the plunger 74 to seal the valve seat 75.
A liquid material introduction channel or route 80 is formed to penetrate vertically from the center of the bottom face of the valve body 71 to a position where the diaphragm 77 on the upper face of the valve seat 75 can come into tight contact. A carrier gas induction route 81, and a mixed gas discharge route 92, which are formed to communicate in a space formed around the valve seat 75 at the time when the diaphragm 77 is brought into tight contact with the upper face of the valve seat 75.
In the control valve 70 of the above constitution, a liquid material 83 from a liquid material tank (not illustrated) is led upward in the liquid material introduction route 80 and introduced into the control valve 70 with the flow rate controlled, and a carrier gas 84 at a high temperature (e.g., 70xc2x0C.) from a carrier gas source (not illustrated) is introduced into the control valve 70 through the carrier gas introducing route 81. The control valve 70 allows the liquid material to be in contact with the high temperature carrier gas 84 to gasify the liquid material 83 into reactant gas, so that this reactant gas is mixed with the carrier gas 84, and this mixed gas 85 is led outside the control valve 70 through the mixed gas discharge route 82.
However, in the above liquid material gasify apparatus, the efficiency of actual use of the carrier gas 84 can be poor, and there is a possibility that the liquid material 83 cannot always be gasified into a stabilized state with good efficiency. This situation can be explained while referring to FIG. 10 and FIG. 11.
Firstly, FIG. 10 shows the flow of the liquid material 83 and the carrier gas 84 in an open state of the valve seat 75, in which the carrier gas 84, introduced into the lower space 79 through the carrier gas induction route 81 flows between the upper surface of the valve seat 75 and the diaphragm 77, as shown by arrow marks 84a to come into contact across the surface of the liquid material 83 which has been guided upward in the liquid material induction route 80. During this operation, a major part of the carrier gas 84 flows in such a manner to be diverted along the perimeter of the valve seat 75 and the body projection 76 underneath, as shown in arrow marks 84b. As a result of such diversion of flow, the introduced high temperature carrier gas 84 does not necessarily make a major contribution to an acceleration of the gasification of the liquid material 83, and accordingly, the partial pressure above the liquid surface may come to a nearly saturated condition, so that condensation is apt to be formed.
In the above liquid material gasifying apparatus, there is a possible drawback that, when the amount of induction of the liquid material 83 into the control valve 70 increases, gasification of such material will not be stable. That is, when a change in the gas flow from the control valve 70 was observed at time periods of having increased stepwise amounts of induction of the liquid material 83 into the control valve 70 while retaining the amount of induction of the carrier gas 84 constant, the results as shown in FIG., 11 were obtained.
In FIG. 11, the mark a shows an amount of induction of the carrier gas 84, which is in this example is 2000 cc/min. And, the mark b shows the amount of induction of the liquid material (e.g., ethanol) 83, which is in this example changed stepwise from 0.2 cc/min. to 1.0 cc/min. Further, the mark c represents a change in flow volume of the gas led out from the control valve 70. From this FIG. 11, it can be seen that the gas flow volume changes over a relatively stabilized manner when the induction amount of ethanol 83 is relatively small, but when the induction amount increases, overshooting or wide fluctuations may occur.
An object of the present invention is to provide a method for gasifying a liquid material and an apparatus thereof so that gasification of a liquid material such as a reactant can be accomplished efficiently and in a stabilized manner at all times.
In order to attain the above object, a method for gasifying a liquid material comprises mixing or entraining a liquid material and a carrier gas while providing flow control in a gas-liquid mixing unit of a control valve provided with a liquid flow control function, and discharging the gas-liquid mixture from a nozzle formed in the vicinity of the flow control unit to fully gasify the liquid material at a reduced pressure level.
An apparatus for practicing the above liquid material gasifying method includes a liquid material supply line equipped with a liquid tank and a flow meter for measuring the flow of the liquid material from the liquid tank and a carrier gas supply line equipped with a carrier gas supply source and a flow control apparatus for controlling the flow of the carrier gas. Each supply line is connected with the control valve independently from each other. A gas-liquid mixing unit and a nozzle unit are formed in close relationship to each other in the control valve, so that the liquid material introduced into the control valve by the above liquid material supply line is released into the carrier gas by an annular gap between a diaphragm and a valve seat. Thus, the liquid material is at a higher pressure than the carrier gas and is released radially inward in controlled discrete amounts to mix with the carrier gas within a mixing channel. Heat can be supplied to both the nozzle unit and the valve seat to raise the temperature of the liquid material. The carrier gas is introduced into the mixing channel of the control valve by the carrier gas supply line while controlling the flow volume, the gas-liquid mixture formed at this time is discharged from the above nozzle to gasify the liquid material at a reduced pressure level, and the gas formed by gasification, along with the carrier gas, is taken out from the gas discharge route on the downstream side of the nozzle.
Flow control of the liquid material in the above control valve may be made based on the output of a flow meter for the liquid or the output of the flow meter for the gas which is provided on the gas supply line.
In this invention, the liquid material and the carrier gas are mixed while controlling the flow in the gas and liquid mixing unit in the control valve equipped with a liquid flow control function, and the gas-liquid mixture can be subjected to reduced pressure instantly at the nozzle, so that the liquid material can be gasified in good efficiency and in a stabilized condition.